今天逆向一个android RSA 加密 java,python都无法还原加密函数。
百思不得骑姐，发量又少了。
搜索N久找到参考资料：
https://blog.csdn.net/weixin_42489404/article/details/98024121

OK！！！！！！

android测试没有问题
java 报错(请知道解决办法的告知下)
错误:java.lang.Exception: java.security.InvalidKeyException: RSA keys must be at least 512 bits long

android 代码如下:

import java.security.KeyFactory;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;

public final class RSA {
    public static final String ALGORITHM_RSA = "RSA";
    
    public static String D(String msg, String n, String e) throws Exception {
        Cipher instance = Cipher.getInstance(ALGORITHM_RSA);
        instance.init(1, bu(str2, str3)); // 生成公钥
        byte[] doFinal = instance.doFinal(str.getBytes());
        StringBuffer stringBuffer = new StringBuffer();
        for (byte b : doFinal) {
            stringBuffer.append(Integer.toString((b & 255) + 256, 16).substring(1));
        }
        return stringBuffer.toString();
    }
    
    // getPublicKey
    private static RSAPublicKey bu(String modulus, String exponent) throws Exception {
        try {
            KeySpec keySpec = new RSAPublicKeySpec(new BigInteger(modulus, 16), new BigInteger(exponent, 16));
            return (RSAPublicKey) KeyFactory.getInstance(ALGORITHM_RSA).generatePublic(keySpec);
        } catch (InvalidKeySpecException e2) {
            throw new Exception(e2.getMessage());
        }
    }
    
    public static String getTest(){
        String retPass, password, e, n;
        password = "2222";
        n = "ab09797f5408c4e1b43e985571db37a6ace935d5b498877f84634ccc61ddbaad";
        e = "10001";
        // 正确结果:8fafd167efa96567cb193c73738d41b9b0a113ae86cdc1c019682c32cb91e05f
        try {
            retPass = RSA.D(password, n, e);
        } catch (Exception e1) {
            retPass = "错误:" + e1;
            e1.printStackTrace();
        }
        return retPass;
    }
  

python 代码：

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Time    : 2022/3/19 10:51
# @Site    : 
# @File    : res1.py
# @Software: PyCharm


import rsa
import base64
from Crypto.PublicKey import RSA


class RSA_ECB_Nopadding:
    def __init__(self, size, n, e):
        self.n = n
        self.e = e

        self.size = size

    def _toBin(self, s):
        """可能有些编码扩展位数"""
        b = bytes(s.encode())

        if self.size > 0:
            for i in range(self.size - len(b)):
                b += b'\0'

        return b

    def encrypt(self, message):
        kLen = rsa.common.byte_size(self.n)
        msg = self._toBin(message)
        _b = rsa.transform.bytes2int(msg)
        _i = rsa.core.encrypt_int(_b, self.e, self.n)
        result = rsa.transform.int2bytes(_i, kLen)
        return result.hex().lower()


class RSA_ECB_Nopadding_str(RSA_ECB_Nopadding):
    def __init__(self, size, key):
        self.pubkey = RSA.importKey(base64.b64decode(key))
        super().__init__(size, self.pubkey.n, self.pubkey.e)


if __name__ == '__main__':
    message = '2222'

    n = b"ab09797f5408c4e1b43e985571db37a6ace935d5b498877f84634ccc61ddbaad"
    e = b"10001"
    # 8fafd167efa96567cb193c73738d41b9b0a113ae86cdc1c019682c32cb91e05f

    n = int(n, 16)
    e = int(e, 16)
    rsaA = RSA_ECB_Nopadding(1, n, e)
    print(rsaA.encrypt(message))

    // message = '{"code":"123451","clienttime":1564560057}'
    // pubkey = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQD2DT4odzkDd7hMlZ7djdZQH12j38nKxriINW1MGjMry3tXheya113xwmbBOwN0GA4zTwKFauFJRzcsD0nDFq1eaatcFKeDF25R4dnQRX+4BdTwFVS8lIb8nJMluSBwK+i4Z3VF+gfZ0AqQOXda6lJ4jPBt9Ep7VXEAHXUDn9JM8wIDAQAB"
    // rsaA = RSA_ECB_Nopadding_str(128, pubkey)
    // print(rsaA.encrypt(message))